1. Field of the Invention
The present invention relates to a suspension structure for a work machine such as a farm tractor or the like.
2. Description of the Related Art
Farm tractors, which constitute one example of a work machine, include tractors that have a front-wheel suspension mechanism, as disclosed, for example, in U.S. Pat. No. 6,145,859. Suspension mechanisms are generally mechanisms which absorb indentations and protrusions in the ground surface by operating on the raising side and lowering side in accordance with such indentations and protrusions in the ground surface, and thus improve the riding comfort.
Because of numerous indentations and protrusions in the operating area over which the work vehicle runs compared to paved roadways, and because a working apparatus is usually mounted on a work vehicle, the operating position of the suspension mechanism may be displaced from the target range on the body raising side or body lowering side (when the operating position of the suspension mechanism is positioned in the target range, the vehicle height is in a specified height range). Consequently, the vehicle height varies from the specified height range.
In this case, in a work vehicle, it is desirable that variations in the vehicle height be minimized and that the vehicle height be maintained in a specified height range. Accordingly, a mechanism (operation changing unit) is provided for moving the operating position of the suspension mechanism toward the target range in cases where the operating position of the suspension mechanism is displaced on the body raising side or the body lowering side as described above, and this is constructed so that the vehicle height is maintained as far as possible in the specified height range.